By Will Dunham
WASHINGTON (Reuters) - Here's some useful advice for the world's ants: Whatever you do, stay away from the "bone-house wasp."
Scientists said on Wednesday they have identified a new species of spider wasp in southeastern China with grim conduct unlike any other creature. It crams the outermost chamber of the nests it builds for its offspring with piles of dead ants.
The female wasps do not hunt the ants for food, instead using the carcasses apparently to frighten off nest invaders.
"Most of the ant specimens belong to a big ant species with a powerful sting. So the female wasp has a certain risk of getting injured or killed," said Michael Staab, a biologist at the University of Freiburg in Germany, whose study was published in the scientific journal PLOS ONE.
Centuries ago, the Aztecs and other Mesoamerican civilizations erected in their cities massive skull racks displaying stacks of the severed heads of sacrificial victims as well as sculpted skulls - monuments certain to inspire dread.
The wasps may be doing something comparable.
"It might work similarly to the skull racks, just not by vision but by scent. The ant chamber may give the wasp's nest the scent of a fierce ant colony - and the nest is thus avoided by natural enemies," Staab said.
The scientists gave the previously unknown species a fittingly macabre name: Deuteragenia ossarium, or "bone-house wasp," after an ossuary, a depository for the bones of the dead.
"Our discovery gives a striking example of the fascinating strategies of offspring protection that have evolved in animals, particularly in insects," Staab said.
Staab said when he first saw one of the ant-filled chambers, he also thought of the ancient Great Wall of China, which protected the Chinese Empire from attacks by enemies just like the ant wall protects the wasp's offspring from nest invaders.
Michael Ohl, a biologist and entomologist at the Museum für Naturkunde in Berlin, added: "We don't know of any similar behavior in the animal kingdom, where dead bodies of another species are used to protect the offspring."
The wasps, discovered in subtropical Chinese forests during a forest diversity study, are black with a brown spot on their wings. Females are up to six-tenths of an inch long (15 mm). The males are a bit smaller and have a white spot on their faces.
Adults feed on pollen and nectar. But the females hunt spiders larger than themselves as food for their offspring, unleashing a paralyzing sting and then dragging or flying the victim to the nest.
The wasps build nests in hollow, above-ground cavities in forest vegetation like the empty tunnels of wood-dwelling beetle larvae. The nest consists of a series of individual cells made by the females, each containing a single wasp egg deposited on a paralyzed spider that will serve as food for the larvae.
The outermost chamber that seals off the nest from the outside world is where the wasps build a special vault packed with the ant corpses.
(Reporting by Will Dunham; Editing by Tom Brown)